Digital watermark embedding apparatus and method, and computer program

ABSTRACT

A digital watermark embedding apparatus divides data to be watermarked into a plurality of data areas on the basis of data characteristics, in time series, or on the basis of user selection and performs digital watermark embedding in which different algorithms are applied to the separate data areas. Unlike schemes that embed digital watermarks using an algorithm that is uniform with all data areas, a digital watermark can be embedded in accordance with each data area of an image. When the algorithm is selected in accordance with user input, the embedding algorithm can be selected in accordance with the characteristics of the human vision or auditory sense. Image/audio quality control and detection performance improvement are thus made possible, and deterioration in data quality can be prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to technology for embedding/readingadditional information such as copyright information and editinginformation into/from various data such as image data including movingimages and still images, music data, and audio data. More particularly,the present invention relates to a digital watermark embedding (may alsobe referred to as “data hiding”) apparatus and method and a computerprogram for embedding a digital watermark as additional informationimperceptible to normal visual or auditory observation into image dataor audio data.

2. Description of the Related Art

As digital technology progresses, digital recorder/players that do notcause deterioration in image quality and sound quality due to repetitiverecording and playing have become widely used. At the same time, varioustypes of digital content such as images and music content have becomedistributable through media such as digital VCRs (videocassetterecorders), DVDs (digital versatile disks), and CD (compact discs) andnetworks.

Unlike analog recording and playing, digital recording and playing donot cause deterioration of data even when recording and playing arerepeatedly performed. As a result, the same quality as that of theoriginal data can be maintained. The widely spread use of digitalrecording and playing technology allows for an excess of illegalcopying. This is a serious problem in view of copyright protection.

In order to protect digital content against copyright infringement byillegal copying, the following scheme is devised. Specifically, thescheme involves adding copy control information to digital content,reading the copy control information when the content is recorded orplayed, and performing processing in accordance with the read copycontrol information, thus preventing illegal copying.

There are various content control schemes. A typical scheme employs, forexample, a copy generation management system (CGMS). For an analog videosignal (referred to as CGMS-A), the CGMS scheme superimposes copycontrol information, that is, two bits of 20-bit additional informationto be superimposed on an effective video portion of a specifichorizontal period, e.g., the 20th horizontal period in case of an NTSCsignal, in a vertical blanking interval of a luminance signal. For adigital video signal (referred to as CGMS-D), the CGMS scheme transmitsthe digital video signal (digital video data) and two bits of copycontrol information serving as additional information to be insertedinto the digital video data.

The two-bit information used in the CGMS scheme (referred to as CGMSinformation) has the following meanings: “00” means that copying ispermitted, “10” means that one copying is permitted (one generation ispermitted), and “11” means that copying is prohibited (copying isabsolutely prohibited).

The CGMS scheme described above is an example of a typical copy controlscheme. There are other schemes for protecting content copyright. Forexample, digital broadcasting performed by a broadcast station stores adigital copy control descriptor in program schedule information, thatis, service information (SI), included in a transport stream (TS) packetforming digital data. When recording data received by a receiver in arecorder, copy generation control in accordance with the descriptor isperformed.

The foregoing control information is added as bit data to the header ofcontent and cannot completely eliminate possible illegal alteration ofthe added data. Digital watermarking is advantageous in eliminating thepossibility of data alteration. When content (image data or audio data)is normally played, a digital watermark is imperceptible to vision andauditory senses. Digital watermarks can only be detected/embedded byexecution of a specific algorithm or processing by a specific device. Adigital watermark is detected when content is processed by a receiver orrecorder/player, and processing in accordance with the digital watermarkis performed, thus making more reliable control possible.

Information that can be embedded in content by digital watermarkingincludes not only the above-described copy control information, but alsovarious information such as content copyright information, contentprocessing information, content format information, content editinginformation, and content playing information.

Information such as a digital watermark that is directly superimposed onan information signal has a strong alteration resistance and is expectedto serve as secure additional information. In digital watermarkingtechnology, the quality of a watermarked image may become a problem.Since digital watermarking performs direct signal processing of data tobe watermarked (e.g., an image), the quality of the image maydeteriorate or the statistic characteristics of the image may be biased,leading to deterioration of the original image. Digital watermarkingthat does not cause adverse effects on content is highly demanded.

An example of a known method for preventing deterioration of originaldata involves setting digital watermark embedding parameters inindividual data areas in the original data such as an image to bewatermarked, and subsequently, again setting a digital watermarksuperimposing level adjusting parameter (global parameter) in the entiredata area taking into consideration the deterioration in image quality.

There are various methods for controlling embedding of digitalwatermarks. In one method, an amount embedded is increased by utilizingthe characteristics of an image. In another method, a digital watermarkis embedded at the minimum embedding level so that priority may be givento image quality. There is not yet a digital watermark embeddingalgorithm, commonly applicable to all information signals such as imageor audio data to be watermarked, for both achieving a sufficient digitalwatermark detecting accuracy and preventing deterioration in imagequality. By embedding a digital watermark, the quality of a data signalsuch as image or audio data may deteriorate, or the reliability ofdetecting an embedded digital watermark may be reduced.

In the foregoing digital watermark superimposing level controllingmethod using the global parameter, a first algorithm for determininginitial embedding parameters determines substantially an optimal levelof superimposing a digital watermark in each data area. Subsequently,the final adjustment involving the global parameter is performed. Theoptimal parameters initialized by the first algorithm in individual dataareas are forcedly changed by setting the global parameter that takesinto consideration deterioration in image quality.

Setting the global parameter may not be favorable in view of digitalwatermark detection. In other words, the initial optimal parameters areset so as to maintain the superimposing level that ensures digitalwatermark detection. When the initial optimal parameters are changed bysetting the global parameter, the sufficient detection level may not beachieved.

SUMMARY OF THE INVENTION

In order to solve the above problems encountered with the related art,it is an object of the present invention to provide a digital watermarkembedding apparatus and method and a computer program for performingdigital watermark embedding by selectively applying various differentdigital watermark embedding algorithms in accordance with individualdata areas in data to be watermarked, thus lessening qualitydeterioration caused by additional information (digital watermarks)embedded in information signals such as image or audio data and ensuringreliable detection of the additional information.

According to a first aspect of the present invention, a digitalwatermark embedding apparatus for performing digital watermark embeddingis provided including a superimposing portion selecting unit fordividing data to be watermarked into data areas; a superimposing leveldetermining unit for selecting and determining beforehand which digitalwatermark embedding algorithm to apply to each of the data areasgenerated by the superimposing portion selecting unit from among aplurality of applicable algorithms; a digital watermark generating unitfor generating digital watermark information based on additionalinformation to be embedded as a digital watermark; a digital watermarklevel controlling unit for generating, on the basis of the digitalwatermark information generated by the digital watermark generatingunit, a digital watermark pattern in which the digital watermarkembedding algorithm determined by the superimposing level determiningunit is applied; and a digital watermark superimposing unit forembedding the digital watermark pattern output by the digital watermarklevel controlling unit into the data to be watermarked.

The digital watermark embedding apparatus may further include a userinput unit for inputting an instruction, and the algorithm may beselected by the superimposing level determining unit on the basis of theinstruction input from the user input unit.

The superimposing portion selecting unit may divide the data to bewatermarked into the data areas on the basis of frequencycharacteristics, and the superimposing level determining unit may selectand determine beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of thefrequency characteristics from among the plurality of applicablealgorithms.

The superimposing portion selecting unit may divide the data to bewatermarked into the data areas on the basis of edge area determination,and the superimposing level determining unit may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated on the basis of the edge area fromamong the plurality of applicable algorithms.

The superimposing portion selecting unit may divide the data to bewatermarked into the data areas in units of time-series data frames, andthe superimposing level determining unit may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated on the basis of the data frames fromamong the plurality of applicable algorithms.

The superimposing portion selecting unit may divide the data to bewatermarked into the data areas on the basis of space positioninformation, and the superimposing level determining unit may select anddetermine beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of the spaceposition information from among the plurality of applicable algorithms.

The superimposing level determining unit may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated by the superimposing portion selectingunit from among the plurality of applicable algorithms, and theplurality of algorithms may include a plurality of algorithms forembedding digital watermarks at different digital watermark embeddinglevels.

The superimposing portion selecting unit may perform data area divisionof data subjected to signal transformation including at least one offiltering, encoding, orthogonal transformation, and compression.

According to a second aspect of the present invention, a digitalwatermark embedding method for performing digital watermark embedding isprovided including a superimposing portion selecting step of dividingdata to be watermarked into data areas; a superimposing leveldetermining step of selecting and determining beforehand which digitalwatermark embedding algorithm to apply to each of the data areasgenerated in the superimposing portion selecting step from among aplurality of applicable algorithms; a digital watermark generating stepof generating digital watermark information based on additionalinformation to be embedded as a digital watermark; a digital watermarklevel controlling step of generating, on the basis of the digitalwatermark information generated in the digital watermark generatingstep, a digital watermark pattern in which the digital watermarkembedding algorithm determined in the superimposing level determiningstep is applied; and a digital watermark superimposing step of embeddingthe digital watermark pattern output in the digital watermark levelcontrolling step into the data to be watermarked.

The digital watermark embedding method may further include a user inputstep of inputting an instruction, and the algorithm may be selected inthe superimposing level determining step on the basis of the instructioninput in the user input step.

The superimposing portion selecting step may divide the data to bewatermarked into the data areas on the basis of frequencycharacteristics, and the superimposing level determining step may selectand determine beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of thefrequency characteristics from among the plurality of applicablealgorithms.

The superimposing portion selecting step may divide the data to bewatermarked into the data areas on the basis of edge area determination,and the superimposing level determining step may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated on the basis of the edge area fromamong the plurality of applicable algorithms.

The superimposing portion selecting step may divide the data to bewatermarked into the data areas in units of time-series data frames, andthe superimposing level determining step may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated on the basis of the data frames fromamong the plurality of applicable algorithms.

The superimposing portion selecting step may divide the data to bewatermarked into the data areas on the basis of space positioninformation, and the superimposing level determining step may select anddetermine beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of the spaceposition information from among the plurality of applicable algorithms.

The superimposing level determining step may select and determinebeforehand the digital watermark embedding algorithm to be applied toeach of the data areas generated in the superimposing portion selectingstep from among the plurality of applicable algorithms, and theplurality of algorithms may include a plurality of algorithms forembedding digital watermarks at different digital watermark embeddinglevels.

The superimposing portion selecting step may perform data area divisionof data subjected to signal transformation including at least one offiltering, encoding, orthogonal transformation, and compression.

According to a third aspect of the present invention, a computer programfor performing digital watermark embedding is provided including asuperimposing portion selecting step of dividing data to be watermarkedinto data areas; a superimposing level determining step of selecting anddetermining beforehand which digital watermark embedding algorithm toapply to each of the data areas generated in the superimposing portionselecting step from among a plurality of applicable algorithms; adigital watermark generating step of generating digital watermarkinformation based on additional information to be embedded as a digitalwatermark; a digital watermark level controlling step of generating, onthe basis of the digital watermark information generated in the digitalwatermark generating step, a digital watermark pattern in which thedigital watermark embedding algorithm determined in the superimposinglevel determining step is applied; and a digital watermark superimposingstep of embedding the digital watermark pattern output in the digitalwatermark level controlling step into the data to be watermarked.

The computer program of the present invention can be provided by variouscomputer-readable storage media, such as a CD, FD (floppy disk), and MO(magneto-optical disk), or by various communications media such as anetwork for providing the computer program to a general-purpose computersystem that can execute various pieces of program code. The provision ofthe program in a computer readable format enables the computer system toperform processing in accordance with the program.

According to the present invention, a digital watermark embeddingapparatus of the present invention has various advantages as describedbelow. The digital watermark embedding apparatus divides data to bewatermarked into a plurality of data areas on the basis of thecharacteristics of the data, in time series, or depending on userselection, and embeds digital watermarks in which different algorithmsare applied to the data areas. Unlike schemes that embed a digitalwatermark by applying a uniform algorithm to each data area, the digitalwatermark embedding apparatus of the present invention can performdigital watermark embedding in accordance with each data area in animage.

Also, the algorithm can be selected in accordance with user input. Sincethe embedding algorithm can be selected in accordance with thecharacteristics of the human vision or auditory sense, imagequality/sound quality control and detection performance improvement aremade possible. The deterioration in data quality can be minimized andprevented. When it is difficult to embed a digital watermark into aninformation signal by applying one algorithm, a different algorithm canbe applied. Thus, appropriate embedding based on data characteristicscan be performed. A digital watermark can be embedded into data to bewatermarked while maintaining the quality of the data, that is, theimage quality in case of an image or the sound quality in case of audiodata.

According to the present invention, unlike schemes that uniformly add aglobal parameter to the entire data, the algorithm in accordance witheach data area can be arbitrarily set. Thus, the detection accuracy canbe maintained, leading to the improvement of detection reliability andstability.

According to the present invention, protection against attacks such asillegal reading and alteration of embedded digital watermark informationcan be enhanced by using a plurality of digital watermark embeddingalgorithms. Algorithms having different attack resistances are selectedin the time, spatial, and frequency domains and used to perform digitalwatermark embedding. Even when the digital watermark information in onedomain is attacked, the digital watermark information in the otherdomains cannot be read or altered. Thus, the detection of the digitalwatermark information by a legal detector can be ensured. Accordingly,digital watermarking becomes more reliable and robust.

Further objects, features, and advantages of the present invention willbecome apparent from the following description of the preferredembodiments with reference to the attached drawings. The word “system”in this specification refers to the logical integrated configurationincluding a plurality of apparatuses and is not limited to apparatusesin the same casing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of the configuration of adigital watermark embedding apparatus of the present invention;

FIG. 2 is a block diagram of an example of the configuration of asuperimposing portion selector of the digital watermark embeddingapparatus of the present invention;

FIG. 3 is a block diagram of an example of the configuration of thesuperimposing portion selector of the digital watermark embeddingapparatus of the present invention;

FIG. 4 is a block diagram of an example of the configuration of thesuperimposing portion selector of the digital watermark embeddingapparatus of the present invention;

FIG. 5 is a block diagram of an example of the configuration of thesuperimposing portion selector of the digital watermark embeddingapparatus of the present invention;

FIG. 6 is a table showing examples of algorithms selected by asuperimposing level determination unit of the digital watermarkembedding apparatus of the present invention;

FIG. 7 is a diagram describing relative frequency distributions of innerproducts of digital watermark patterns;

FIG. 8 is a diagram describing a determination reference for determiningwhether or not data is watermarked;

FIG. 9 illustrates embedding of a plurality of digital watermarkpatterns into an image;

FIG. 10 illustrates division of an original image into sub-areas;

FIG. 11 illustrates allocation of the same information bit to aplurality of sub-areas;

FIG. 12 illustrates a process performed by a digital watermark detector;

FIG. 13 is a table showing combinations of algorithms selected by thesuperimposing level determination unit of the digital watermarkembedding apparatus; and

FIG. 14 is a diagram of the configuration of a system for performingdigital watermark embedding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, a digital watermarkembedding apparatus and method according to the present invention willnow be described in detail.

FIG. 1 shows an example of the configuration of a digital watermarkpattern embedding apparatus for embedding a digital watermark pattern indata. Referring to FIG. 1, the embedding of a digital watermark patternin an image will be schematically described. The details of processingby each processor will be described later.

Data to be watermarked 101 includes various types of data, such as animage, audio data, or program data. The data to be watermarked 101 is,for example, an image read from a hard disk or a storage medium such asa DVD or an image supplied from an image scanning device such as ascanner or a digital camera.

The data to be watermarked 101 is output to a superimposing portionselector 102 of the digital watermark embedding apparatus. Thesuperimposing portion selector 102 divides data to be watermarked 101,which is an input signal, into a plurality of portions on the basis ofcharacteristics of the data to be watermarked 101. For example, whenimage data is to be watermarked 101, the image data is divided into anedge area and the other (edgeless) area or into a high frequency areaand a low frequency area. An edge area or high frequency area of imagedata has a high rate of change in pixel values (pixels forming theimage) in a predetermined area. Generally, when a digital watermark isembedded in such an area at a high level, the embedded digital watermarkmay not be perceptible. In contrast, a low frequency area has uniformpixel values. For example, the “sky” is such an area having uniformluminance and color. When a digital watermark is embedded in such anarea at a high embedding intensity (level), the digital watermarkbecomes perceptible to normal observation. In general, the digitalwatermark is embedded in such an area at a reduced embedding intensity(level).

The superimposing portion selector 102 analyzes the data to bewatermarked 101 and divides the data to be watermarked 101 into aplurality of areas, such as a high frequency area and a low frequencyarea, on the basis of characteristics of the data to be watermarked 101.The specific processing by the superimposing portion selector 102 willbe described later.

The plurality of data areas generated by the superimposing portionselector 102 is output to a superimposing level determination unit 103.The superimposing level determination unit 103 determines whichalgorithm to apply from among a plurality of prepared digital watermarkembedding algorithms. For example, the superimposing level determinationunit 103 determines the digital watermark embedding algorithm to beapplied to each of the data areas generated by the superimposing portionselector 102 on the basis of user input from a user input unit 111 orpreset information. The application processing of the plurality ofalgorithms will be described in detail in the later part of thedescription. The superimposing level determination unit 103 outputssuperimposing level information based on the determined algorithm to adigital watermark level controller 106.

A digital watermark generator 107 modulates additional information to beembedded as a digital watermark 110 and generates digital watermarkinformation. The processing performed by the digital watermark generator107 involves modulation based on various control information, such asimage division information and bit sequence information, used forembedding into an image a digital watermark corresponding to the bitinformation 110 forming various additional information, such as copycontrol information, copyright information, and editing information, tobe embedded into data.

The digital watermark information generated by the digital watermarkgenerator 107 is output to the digital watermark level controller 106.The digital watermark level controller 106 receives the digitalwatermark information generated by the digital watermark generator 107and superimposing level information based on the digital watermarkembedding algorithm selected for each data area by the superimposinglevel determination unit 103, adjusts the digital watermark embeddinglevel for each data area, and outputs a digital watermark pattern whoseembedding level is adjusted by applying the algorithm determined by thesuperimposing level determination unit 103 in each data area to adigital watermark superimposing unit 108.

The digital watermark superimposing unit 108 receives the data to bewatermarked 101 and the level-adjusted digital watermark pattern fromthe digital watermark level controller 106, embeds the digital watermarkinto the data to be watermarked 101, and outputs the resulting data aswatermarked data 109.

This is the outline of the digital watermark embedding processing of thepresent invention. The details of processing performed by each processorwill now be described.

Processing by Superimposing Portion Selector

A specific example of processing performed by the superimposing portionselector 102 shown in FIG. 1 will now be described. The superimposingportion selector 102 analyzes the data to be watermarked 101 and dividesthe data to be watermarked 101 into a plurality of portions on the basisof characteristics of the data to be watermarked 101.

As described above, when the data to be watermarked 101, which is aninput signal, is image data, the superimposing portion selector 102divides the image data into an edge area and the other (edgeless) areaor into a high frequency area and a low frequency area.

FIG. 2 shows an example of the configuration of a superimposing portionselector for dividing data into data areas according to frequencies. Inthis example, the superimposing portion selector includes a low-passfilter (LPF) 201, a band-pass filter (BPF) 202, and a high-pass filter(HPF) 203. Data to be watermarked is input to the filters 201 to 203.The filters 201 to 203 output data in predetermined frequency areas,that is, a low frequency area, a high frequency area, and anintermediate frequency area. The separate pieces of data are output tothe superimposing level determination unit 103 shown in FIG. 1. Thesuperimposing level determination unit 103 determines the digitalwatermark embedding algorithm to be applied to each of the separatepieces of data.

FIG. 3 shows an example of the configuration of a superimposing portionselector for dividing data into data areas on the basis of edgedetection. In this example, the superimposing portion selector includesan edge detector 301. Data to be watermarked is input to the edgedetector 301. The edge detector 301 can be formed using a frequencydetector. The edge detector 301 divides the input data into an edge areaand an edgeless area, which are in turn output to the superimposinglevel determination unit 103 shown in FIG. 1. The superimposing leveldetermination unit 103 determines the digital watermark embeddingalgorithm to be applied to each of the separate pieces of data.

When input data serving as data to be watermarked is a moving image, asuperimposing portion selector can divide data frames, which are inputin time series and which form the moving image, into groups of apredetermined number of data frames or into groups at predetermined timeintervals. FIG. 4 shows an example of superimposing portion selectionprocessing by frame division. Assuming that the data frames forming themoving image are input starting from frame k, as shown in FIG. 4, thesuperimposing portion selector divides the frames into groups of apredetermined number of frames or into groups at predetermined timeintervals. The separate groups, which are referred to as selected dataA, B, C, and so forth, are output to the superimposing leveldetermination unit 103 shown in FIG. 1. The superimposing leveldetermination unit 103 determines the digital watermark embeddingalgorithm to be applied to each of the separate groups of data.

In addition to dividing the frames according to the number of frames ortime, the frame division can be performed in various manners. Forexample, a scene change or a breakpoint between images or audio data isdetected, and the frames are divided at the scene change or breakpoint.Alternatively, the frame division can be performed on the basis of afrequency component distribution, edge-peak distribution, or timedifference between frames.

Referring to FIG. 5, when input data to be watermarked 501 is imagedata, space division based on space position information can beperformed. In the example shown in FIG. 5, the data to be watermarked501 is divided into four areas a, b, c, and d. The superimposing portionselector divides the image data into a plurality of areas by spacedivision. The separate pieces of data are output to the superimposinglevel determination unit 103 shown in FIG. 1. The superimposing leveldetermination unit 103 determines the digital watermark embeddingalgorithm to be applied to each separate piece of data.

In the example shown in FIG. 5, the image data is divided into spatiallyequal spaces. Alternatively, for example, space division based on thedifferences in output level through a filter can be performed.

The data division by the superimposing portion selector 102 is notlimited to those described in the foregoing examples and can beperformed in various processing manners in accordance with data to bewatermarked. For example, when data to be watermarked is image data, theimage data can be divided in accordance with a luminance level of eachpixel. When data to be watermarked is audio data, the audio data can bedivided into a plurality of portions in accordance with the audio level.

Processing by Superimposing Level Determination Unit

The separate pieces of data generated by the superimposing portionselector 102 are output to the superimposing level determination unit103. The superimposing level determination unit 103 is a processor thatdetermines which algorithm to apply from among a plurality of prepareddigital watermark embedding algorithms. On the basis of an instructioninput from the user input unit 111 or preset information, thesuperimposing level determination unit 103 determines the digitalwatermark embedding algorithm to be applied to each of the separatepieces of data generated by the superimposing portion selector 102.

FIG. 6 shows examples of a plurality of algorithms. In FIG. 6, sixdigital watermark embedding algorithms are shown. Digital watermarkembedding processing embeds bit information forming copy controlinformation, copyright information, and editing information, which serveas additional information to be embedded into data. The digitalwatermark embedding algorithm defines, for example, how datacorresponding to bit 1 or bit 0 is embedded into data such as image oraudio data.

Prior to describing each algorithm shown in FIG. 6, an example in whicha digital watermark is embedded into image data and the embedded digitalwatermark is detected will now be described. In this example, Prepresents an original image to be watermarked, and L represents adigital watermark pattern to be embedded into the original image P. Thedigital watermark pattern L satisfies the following:Σ_(i,j)L_(i,j)=0  (1)

For example, the original image P and the digital watermark pattern Lare set as follows:

$\begin{matrix}{{P = \begin{pmatrix}21 & 22 & 23 & 25 & 24 \\22 & 24 & 28 & 30 & 26 \\21 & 23 & 27 & 31 & 29 \\22 & 25 & 30 & 30 & 28\end{pmatrix}}{L = \begin{pmatrix}{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1 \\{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1\end{pmatrix}}} & (2)\end{matrix}$

In equations (2), the size of the original image P is set to 5×4 pixelsin order to simplify the description. Images have a characteristic inwhich adjacent pixels generally have similar values. Thus, adjacentelements in the original image P are set to similar values.

The digital watermark embedding processing is performed on the basis ofthe following equation:M=P+L  (3)

wherein M denotes an image generated by embedding the digital watermarkpattern L in the original image P. In the example of equations (2), thevalue M is computed as follows:

$\begin{matrix}\begin{matrix}{M = {P + L}} \\{= {\begin{pmatrix}21 & 22 & 23 & 25 & 24 \\22 & 24 & 28 & 30 & 26 \\21 & 23 & 27 & 31 & 29 \\22 & 25 & 30 & 30 & 28\end{pmatrix} + \begin{pmatrix}{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1 \\{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1\end{pmatrix}}} \\{= \begin{pmatrix}20 & 23 & 22 & 26 & 23 \\23 & 23 & 29 & 29 & 27 \\20 & 24 & 26 & 32 & 28 \\23 & 24 & 31 & 29 & 29\end{pmatrix}}\end{matrix} & (4)\end{matrix}$

The digital watermark detection is performed using the digital watermarkpattern L. The digital watermark detection for the original image Phaving no digital watermark pattern L embedded therein is defined by:s=P·L  (5)

wherein the operator·computes the inner product of the matrices, and sis the inner product of the original image P and the digital watermarkpattern L.

Since the sum total of elements in the digital watermark pattern L iszero (see equation (1)) and adjacent pixels of the image generally havesimilar values, the inner product s is a value near zero. In the exampleillustrated by equations (2), the inner product is:

$\begin{matrix}\begin{matrix}{s = {P \cdot L}} \\{= {\begin{pmatrix}21 & 22 & 23 & 25 & 24 \\22 & 24 & 28 & 30 & 26 \\21 & 23 & 27 & 31 & 29 \\22 & 25 & 30 & 30 & 28\end{pmatrix} \cdot \begin{pmatrix}{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1 \\{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1\end{pmatrix}}} \\{= \begin{matrix}{- 21} & {+ 22} & {- 23} & {+ 25} & {- 24} \\{+ 22} & {- 24} & {+ 28} & {- 30} & {+ 26} \\{- 21} & {+ 23} & {- 27} & {+ 31} & {- 29} \\{+ 22} & {- 25} & {+ 30} & {- 30} & {+ 28}\end{matrix}} \\{= 3}\end{matrix} & (6)\end{matrix}$

A similar calculation is performed for the watermarked image M. Asdescribed above, the digital watermark detection for the watermarkedimage M having the digital watermark pattern L embedded therein isperformed by computing the inner product s′ in accordance with thefollowing equation:

$\begin{matrix}\begin{matrix}{s^{\prime} = {M \cdot L}} \\{= {\left( {P + L} \right) \cdot L}} \\{= {{P \cdot L} + {L \cdot L}}} \\{= {3 + {L \cdot L}}} \\{= {3 + {\begin{pmatrix}{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1 \\{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1\end{pmatrix} \cdot \begin{pmatrix}{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1 \\{- 1} & 1 & {- 1} & 1 & {- 1} \\1 & {- 1} & 1 & {- 1} & 1\end{pmatrix}}}} \\{= {3 + \begin{matrix}{+ \left( 1 \right.} & {+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {+ 1} & {+ 1} & {+ 1} & \left. {+ 1} \right)\end{matrix}}} \\{= {3 + 20}}\end{matrix} & (7)\end{matrix}$

Whereas the inner product s of the original image P and the digitalwatermark pattern L is a value near zero, the inner product s′ of thewatermarked image M and the digital watermark pattern L is a value nearthe inner product of the digital watermark pattern L itself, that is, avalue near the following expression:L·L  (8)

The inner product L·L can be used as a scale for measuring the intensityof embedding a digital watermark. When the inner product L·L, which isthe target for embedding a digital watermark, is large, the digitalwatermark embedding intensity is represented as being “high”; when theinner product L·L is small, the digital watermark embedding intensity isrepresented as being “low”.

Also, when the absolute value of the inner product s of the originalimage P and the digital watermark pattern L or the inner product s′ ofthe watermarked image M and the digital watermark pattern L is large,the digital watermark detecting intensity is represented as being“high”; when the absolute value of the inner product s or the innerproduct s′ is small, the digital watermark detecting intensity isrepresented as being “low”.

When the digital watermark detecting intensity is high, the correlationbetween the image and the digital watermark pattern may be representedas being “large” or “high”. When the digital watermark detectingintensity is low, the correlation between the image and the digitalwatermark may be represented as being “small” or “low”.

The inner product s of the original image P and the digital watermarkpattern L and the inner product s′ of the watermarked image M and thedigital watermark pattern L are computed in various images, and therelative frequency distributions thereof are represented by probabilitydensity functions f and f′, respectively, as shown in FIG. 7.

Whether or not an image is watermarked is determined on the basis of thefact that the inner products s of the unwatermarked image P and thedigital watermark pattern L are distributed around zero and the factthat the inner products s′ of the watermarked image M and the digitalwatermark pattern L are distributed around L·L, which is the innerproduct of the digital watermark pattern L itself. The inner product s″of an image to be checked for a digital watermark and the digitalwatermark pattern L is computed, and the inner product s″ is comparedwith a threshold (th) to determine the presence of a digital watermark.Specifically, the following expressions are applicable:

-   -   s″<th, then no-watermark    -   s″≧th, then watermarked

The above expressions indicate that if the inner product s″ of the imageto be checked for a digital watermark and the digital watermark patternL is less than the threshold (th), then it is determined that the imageis not watermarked, and if the inner product s″ is greater than or equalto the threshold (th), then it is determined that the image iswatermarked. The expressions are illustrated in FIG. 8.

Methods for embedding multi-bit information as a digital watermark intoan image can be classified into methods using a plurality of digitalwatermark patterns, methods involving division of an image intosub-areas, and methods combining the foregoing two types of methods.

The methods using a plurality of digital watermark patterns can beclassified into three types: methods in which the digital watermarkpatterns are each given a different meaning and exclusively embedded torepresent desired information; methods in which a plurality of digitalwatermark patterns are overlappingly embedded at the same time into animage, whereby desired information is represented by a combination ofthe digital watermark patterns; and methods combining the two types ofmethods. FIG. 9 shows embedding of a plurality of digital watermarkpatterns into an original image.

In the methods in which the digital watermark patterns are each given adifferent meaning and exclusively embedded to represent desiredinformation, when b represents the number of bits of information to beembedded into the image, the number of types of digital watermarkpatterns required n is n=2^(b). In contrast, in the methods in which aplurality of digital watermark patterns are overlappingly embedded atthe same time into an image, whereby desired information is representedby a combination of the digital watermark patterns, the number of typesof digital watermark patterns required n is n=b. The latter typerequires a smaller number of types of digital watermark patterns.However, because a plurality of digital watermark patterns areoverlappingly embedded into the image, appropriate processing to preventdeterioration may often be necessary. In the last method type combiningthe foregoing two types of methods, the number of types of digitalwatermark patterns required n is b≦n≦2^(b), and this method has thefeatures of the two types of methods.

The methods involving division of an image into sub-areas are anothertype of methods for embedding multi-bit information as a digitalwatermark into an image. By assigning a different function to each ofthe sub-areas, a plurality of digital watermarks can exist at the sametime in the image. Various sub-area arrangements are proposed. In thedescription, for example, as shown in FIG. 10, the sub-areas are arrayedin a grid. In FIG. 10, i and j denote non-negative integers.

When an image is divided into sub-areas, the number of partitions iscrucial. When information to be embedded into an image has b bits, theimage may be divided into b sub-areas. Disadvantageously, this methodmay cause a problem because, when various images are to be watermarked,digital watermarking is performed taking into consideration visualcharacteristics of the images. For example, when digital watermarking isperformed such that an edge area of an image is subjected to a highembedding intensity while a flat portion is subjected to a low embeddingintensity, if a sub-area corresponding to a bit happens to be the flatarea, the digital watermark embedded in that sub-area may not bedetectable. If the digital watermark detection for one sub-area fails;even when digital watermarks embedded in the remaining sub-areas aredetected, the combination of the digital watermarks represents nomeaningful information. Dividing an image into sub-areas greater than bis advantageous in that digital watermarks can be stably detected fromvarious images. Even when a sub-area has a very low digital watermarkembedding intensity, if the remaining sub-areas (into which the same bitinformation is embedded) have a sufficient digital watermark patternembedding intensity, the digital watermark can be detected from theentire image.

FIG. 11 shows an example in which an image is divided into sub-areaswhen information to be embedded has eight bits. A plurality of sub-areascorresponding to the same bit is allocated in the image.

FIG. 12 shows an example of the configuration of a digital watermarkdetector for detecting a digital watermark from a watermarked image.Referring to FIG. 12, digital watermark detection processing will now bedescribed.

An image 601 is an example of watermarked data to be checked for adigital watermark. The image data 601 includes various images, such asan image read from a hard disk or a storage medium such as a DVD or animage supplied through a communications system.

A digital watermark pattern generator 603 generates a digital watermarkpattern from a digital watermark pattern generation key of a digitalwatermark pattern generation key storage unit 602. Specifically, thedigital watermark pattern generation key includes image divisioninformation used when a digital watermark pattern is embedded into animage or bit sequence information. The digital watermark patterngeneration key is required for detecting the digital watermark pattern.

A detector 604 uses the digital watermark pattern generated by thedigital watermark pattern generator 603 to detect the digital watermarkin the input image 601. The detection processing involves, as describedabove, determining the correlation between the generated digitalwatermark pattern and the image by the inner product and comparing thecomputed inner product with the threshold (th) (see expressions (9)).When the image has multi-bit information embedded therein as a digitalwatermark, as described with reference to FIGS. 9 to 11, the multi-bitinformation is obtained. The information detected by the detector 604 isoutput as detected information 605.

Referring back to FIG. 6, the digital watermark embedding algorithmapplied by the superimposing level determination unit 103 in the digitalwatermark embedding apparatus of the present invention will now bedescribed. Referring to FIG. 6, the superimposing level determinationunit 103 selects one from among the plurality of algorithms inaccordance with the following equations for each of the data areasgenerated by the foregoing superimposing portion selector 102:L(i,j)=a(a:const.)  (1)L(i,j)=|−1.0 2.0−1.0|  (2)

$\begin{matrix}{{L\left( {i,j} \right)} = \begin{pmatrix}{- 1.0} & {- 1.0} & {- 1.0} \\{- 1.0} & 8.0 & {- 1.0} \\{- 1.0} & {- 1.0} & {- 1.0}\end{pmatrix}} & (3) \\{{L\left( {i,j} \right)} = \begin{pmatrix}{- 0.0} & {- 1.0} & {- 0.0} \\{- 1.0} & 4.0 & {- 1.0} \\{- 0.0} & {- 1.0} & {- 0.0}\end{pmatrix}} & (4)\end{matrix}$L(i,j)=αV(i,j) or αA(t)  (5)CONTROL BY LUMINANCE OR AUDIO LEVEL(6)L(i,j)=αP(m.n)  (10)EMBEDDING IN ACCORDANCE WITH COEFFICIENT VALUE AFTER TRANSFORM  (10)

The algorithm identified by the algorithm identifier (1) (hereinafterreferred to as the algorithm (1)) embeds a constant value a as digitalwatermark embedding bit information. The algorithm (2) adds theintensity (e.g., luminance value change) as information (−1.0, 2.0,−1.0) to three data values (e.g., three horizontal pixel values) in apredetermined direction.

The algorithm (3) is, as described above, a matrix-type digitalwatermark embedding algorithm for embedding an amount of data with anintensity distribution indicated by the algorithm (3) into one centraldata (e.g., a pixel value) and surrounding seven pieces of data (e.g.,pixel values). The algorithm (4) is, as in the algorithm (3), amatrix-type digital watermark embedding algorithm for embedding anamount of data with an intensity distribution indicated by the algorithm(4) into one central data (e.g., a pixel value) and horizontally andvertically adjacent pieces of data (e.g., pixel values).

In the algorithm (5), α is a coefficient value. When data to bewatermarked is image data, the algorithm (5) generates a control valuebased on the predetermined coefficient α relative to the luminance valueof a pixel. When data to be watermarked is audio data, the algorithm (5)generates a control value based on the predetermined coefficient αrelative to an audio level value.

In the algorithm (6), α is a coefficient value, and P(m, n) denotesorthogonally-transformed data to be watermarked. The algorithm (6)generates a control value based on the predetermined coefficient αrelative to the orthogonally transformed data.

The superimposing level determination unit 103 of the digital watermarkembedding apparatus of the present invention determines the algorithm tobe applied to each of the data areas generated by the superimposingportion selector 102 from among the above algorithms (1) to (6). Thedetermination is performed on the basis of user input or presetinformation.

FIG. 13 shows two examples of combinations of selected algorithms. Inthe examples shown in FIG. 13, data to be watermarked is divided intotwo data areas, and different algorithms are applied to the two dataareas.

The data to be watermarked is divided into a first sub area, that is, ahigh frequency (edge) area, and a second sub area, that is, a lowfrequency (flat) area. The division processing is performed by thesuperimposing portion selector 102.

In the first example of algorithm selection, the algorithm (4), which isdescribed using FIG. 6 or equations (10), is applied to the highfrequency (edge) area, and the algorithm (1) is applied to the lowfrequency (flat) area. In the second example of algorithm selection, thealgorithm (3) is applied to the high frequency (edge) area, and thealgorithm (5) is applied to the low frequency (flat) area.

In the examples shown in FIG. 13, the data area is divided into two subareas, and different algorithms are applied to the two sub areas. Whenthe data area is divided into three or more sub areas, processing isperformed to set the algorithm to be applied to each of the sub areas.

Processing by Digital Watermark Level Controller

The digital watermark level controller 106 shown in FIG. 1 receivesdigital watermark information, which is generated by modulating the bitinformation 110 forming the copy control information, copyrightinformation, and editing information from the digital watermarkgenerator 107 and superimposing level information corresponding to thedigital watermark embedding algorithm selected for each data area fromthe superimposing level determination unit 103, performs adjustment ofthe digital watermark embedding level for each data area to generate adigital watermark pattern, and outputs the digital watermark pattern tothe digital watermark superimposing unit 108.

For example, given that bit information generated by the digitalwatermark generator 107 is based on additional information set for animage sub area to be watermarked, and that the superimposing leveldetermination unit 103 selects the first combination of algorithms shownin FIG. 13, when the image area to which the bit information will beadded corresponds to the high frequency (edge) area, the algorithm (4)is applied, and when the image area corresponds to the low frequency(flat), the algorithm (1) is applied. The digital watermark levelcontroller 106 thus generates a digital watermark pattern whose level isadjusted by applying different algorithms to the data areas and outputsthe digital watermark pattern to the digital watermark superimposingunit 108.

The digital watermark superimposing unit 108 receives the data to bewatermarked 101 and the level-adjusted digital watermark pattern fromthe digital watermark level controller 106, embeds (superimposes) thedigital watermark into the data to be watermarked 101, and outputs thewatermarked data 109.

As described above, the digital watermark embedding apparatus of thepresent invention divides data to be watermarked into a plurality ofdata areas on the basis of the characteristics of the data, in timeseries, or depending on user selection and performs digital watermarkembedding in which different algorithms are applied to the data areas.For example, when the algorithm is selected in accordance with userinput, the selected algorithm can be comprehensive, taking intoconsideration not only the characteristics of information signals butalso the characteristics of the human eye. Image quality control anddetection performance improvement are made possible, thus minimizingdeterioration of quality and allowing the human being to manage the-dataquality.

When it is difficult to embed a digital watermark into an informationsignal by applying one algorithm, a different algorithm can be applied.Thus, appropriate embedding based on data characteristics can beperformed. Additional information serving as a digital watermark can beembedded into data to be watermarked while maintaining the quality ofthe data to be watermarked, that is, the image quality in case of animage or the sound quality in case of audio data.

Unlike schemes that uniformly add a global parameter to the entire data,the digital watermark embedding apparatus of the present invention canarbitrarily set the algorithm in accordance with each data area.Detection accuracy can be maintained, and detection reliability andstability are thus improved. Control that accomplishes the image qualityimprovement not involving the deterioration of detection performance ismade possible. Compared with schemes that use a global parameter toperform overall adjustment, the total performance can be ensured by thepresent invention.

In the foregoing embodiment, the data to be watermarked is primarilydescribed using image data as an example. However, the data to bewatermarked may be a video signal, image information, music, an audiosignal, MIDI, and other information signals. An information signal maybe a baesband signal or a compressed signal. The embedding algorithm canbe selected for each sub area of the data to be watermarked, or can beselected in the time or frequency domains. Instead of dividing the datato be embedded into a plurality of pieces, the entire data can bewatermarked using one algorithm. If necessary, in response to a userinstruction, the embedding algorithm can be changed, for example, in thetime domain. In this case, embedding may be switched.

Instead of selecting the digital watermark embedding algorithm inaccordance with a user instruction, the digital watermark embeddingalgorithm may be selected algorithmically. Alternatively, the digitalwatermark embedding algorithm may be selected algorithmically whiletaking into consideration the user selection. Instead of dividing datato be watermarked into sub areas, to which algorithms are applied, onthe basis of the characteristics of the data, the data can be divided onthe basis of positional information or in the time or spatial domain ofthe data. Additional information may be coded by spread spectrum orpatchwork techniques.

The division processing of data to be watermarked may be performed fortransformed data areas in the spatial, frequency, and time domains,which have been subjected to signal transformation including variousfilters, encoding, orthogonal transforms, compression, such as DCT,wavelet transforms, JPEG, MPEG, fractal transforms, ATRACK, MP3, AC3,AAC, ADPCM, CELP, and TwinV.

System Configuration

The series of processes described in the foregoing embodiment can beexecuted by hardware, software, or a combination of both. Whenprocessing is performed by software, a program having recorded aprocessing sequence therein is installed into a memory in a dataprocessor incorporated in dedicated hardware and thus executed, or,alternatively, the program is installed into a general-purpose computercapable of performing various processes and thus executed. When theseries of processes is performed by software, the program forming thesoftware is installed into, for example, a general-purpose computer or aone-chip microcomputer. FIG. 14 shows an example of the systemconfiguration of an apparatus for performing at least one of digitalwatermark generation, embedding, and detection. The configuration shownin FIG. 14 will now be described.

A CPU (Central Processing Unit) 802 actually executes variousapplication programs and an OS (Operating System). A ROM(Read-Only-Memory) 803 stores the programs executed by the CPU 802 andfixed data serving as operation parameters. A RAM (Random Access Memory)804 is used as a storage area or work area for the programs executed bythe CPU 802 and the parameters changing in accordance with the programs.The CPU 802, the ROM 803, the RAM 804, and a hard disk 805 are connectedwith one other by a bus 801 and can transmit data to one another. Also,the CPU 802, ROM 803, RAM 804, and hard disk 805 can transmit data tovarious input/output apparatuses connected to an input/output interface814.

A keyboard 812 and a mouse 813 are operated by a user to input variouscommands to the CPU 802. When inputting command input data, the useroperates the keyboard 812 and mouse 813 and inputs the data via akeyboard/mouse controller 811.

A drive 819 reads/writes a removable recording medium 801 such as afloppy disk, CD-ROM (Compact Disc Read Only Memory), MO (MagnetoOptical) disc, DVD (Digital Versatile Disc), magnetic disk, orsemiconductor memory. The drive 819 reads a program and/or data from theremovable recording medium 810 and/or stores a program and/or data inthe removable recording medium 810.

When a command is input via the input/output interface 814, keyboard812, or mouse 813, the CPU 802 executes a program stored in the ROM 803in accordance with the input command.

Data such as image or audio data to be watermarked or data to be checkedfor a digital watermark in the foregoing embodiment can be input from acamera 8071 or another input device (e.g., a data input device such as ascanner) connected to an input unit 807 or can be input from theremovable recording medium 810 such as the floppy disk, CD-ROM, MO, DVD,magnetic disk, or semiconductor memory. In the present system, audiodata can be input from a microphone 8072. Data received via acommunication unit 808 can be processed as image data to be watermarkedor image data to be checked for a digital watermark.

The CPU 802 may load into the RAM 804 not only programs stored in theROM 803 but also programs stored in the hard disk 805, programstransmitted from a satellite or a network, received by the communicationunit 808, and installed in the hard disk 805, or programs read from theremovable recording medium 810 attached to the drive 809 and installedin the hard disk 805, and may execute the programs.

In the present specification, programs may be processed by a computer orby a plurality of computers in a decentralized manner. Furthermore,programs may be transmitted to a remote computer and executed by theremote computer.

While the present invention has been described in detail with referenceto what are presently considered to be the preferred embodiments, it isto be understood to those skilled in the art that various modificationsand substitutions can be made without departing from the spirit andscope of the present invention. In other words, the present inventionhas been described using the embodiments only for illustration purposesand should not be interpreted in a limited manner. The scope of thepresent invention is to be determined solely by the appended claims.

1. A digital watermark embedding apparatus for performing digitalwatermark embedding, comprising: superimposing portion selecting meansfor dividing each frame of data to be watermarked into a plurality ofdata areas, said superimposing portion selecting means determiningborders of each data area based on data characteristics of each dataarea in the frame; superimposing level determining means for selectingand determining beforehand which digital watermark embedding algorithmto apply to each of the data areas in the frame generated by saidsuperimposing portion selecting means from among a plurality ofdifferent applicable algorithms based on characteristics of each of thedata areas in the frame; digital watermark generating means forgenerating digital watermark information based on additional informationto be embedded as a digital watermark; digital watermark levelcontrolling means for generating, on the basis of the digital watermarkinformation generated by said digital watermark generating means, adigital watermark pattern in which the digital watermark embeddingalgorithm determined by said superimposing level determining means isapplied; and digital watermark superimposing means for embedding thedigital watermark pattern output by said digital watermark levelcontrolling means into the data to be watermarked.
 2. The digitalwatermark embedding apparatus according to claim 1, further comprisinguser input means for inputting an instruction, wherein the algorithm isselected by said superimposing level determining means on the basis ofthe instruction input from the user input means.
 3. The digitalwatermark embedding apparatus according to claim 1, wherein saidsuperimposing portion selecting means divides the data to be watermarkedinto the data areas on the basis of frequency characteristics, and saidsuperimposing level determining means selects and determines beforehandthe digital watermark embedding algorithm to be applied to each of thedata areas generated on the basis of the frequency characteristics fromamong the plurality of applicable algorithms.
 4. The digital watermarkembedding apparatus according to claim 1, wherein said superimposingportion selecting means divides the data to be watermarked into the dataareas on the basis of edge area determination, and said superimposinglevel determining means selects and determines beforehand the digitalwatermark embedding algorithm to be applied to each of the data areasgenerated on the basis of the edge area from among the plurality ofapplicable algorithms.
 5. The digital watermark embedding apparatusaccording to claim 1, wherein said superimposing portion selecting meansdivides the data to be watermarked into the data areas in units oftime-series data frames, and said superimposing level determining meansselects and determines beforehand the digital watermark embeddingalgorithm to be applied to each of the data areas generated on the basisof the data frames from among the plurality of applicable algorithms. 6.The digital watermark embedding apparatus according to claim 1, whereinsaid superimposing portion selecting means divides the data to bewatermarked into the data areas on the basis of space positioninformation, and said superimposing level determining means selects anddetermines beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of the spaceposition information from among the plurality of applicable algorithms.7. The digital watermark embedding apparatus according to claim 1,wherein said superimposing level determining means selects anddetermines beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated by said superimposingportion selecting means from among the plurality of applicablealgorithms, and the plurality of algorithms include a plurality ofalgorithms for embedding digital watermarks at different digitalwatermark embedding levels.
 8. The digital watermark embedding apparatusaccording to claim 1, wherein said superimposing portion selecting meansperforms data area division of data subjected to signal transformationincluding at least one of filtering, encoding, orthogonaltransformation, and compression.
 9. A digital watermark embedding methodfor performing digital watermark embedding, comprising: a superimposingportion selecting step of dividing each frame of data to be watermarkedinto a plurality of data areas, said superimposing portion selectingstep including determining borders of each data area based on datacharacteristics of each data area in the frame; a superimposing leveldetermining step of selecting and determining beforehand which digitalwatermark embedding algorithm to apply to each of the data areas in theframe generated in said superimposing portion selecting step from amonga plurality of different applicable algorithms based on characteristicsof each of the data areas in the frame; a digital watermark generatingstep of generating digital watermark information based on additionalinformation to be embedded as a digital watermark; a digital watermarklevel controlling step of generating, on the basis of the digitalwatermark information generated in said digital watermark generatingstep, a digital watermark pattern in which the digital watermarkembedding algorithm determined in said superimposing level determiningstep is applied; and a digital watermark superimposing step of embeddingthe digital watermark pattern output in said digital watermark levelcontrolling step into the data to be watermarked.
 10. The digitalwatermark embedding method according to claim 9, further comprising auser input step of inputting an instruction, wherein the algorithm isselected in said superimposing level determining step on the basis ofthe instruction input in the user input step.
 11. The digital watermarkembedding method according to claim 9, wherein said superimposingportion selecting step divides the data to be watermarked into the dataareas on the basis of frequency characteristics, and said superimposinglevel determining step selects and determines beforehand the digitalwatermark embedding algorithm to be applied to each of the data areasgenerated on the basis of the frequency characteristics from among theplurality of applicable algorithms.
 12. The digital watermark embeddingmethod according to claim 9, wherein said superimposing portionselecting step divides the data to be watermarked into the data areas onthe basis of edge area determination, and said superimposing leveldetermining step selects and determines beforehand the digital watermarkembedding algorithm to be applied to each of the data areas generated onthe basis of the edge area from among the plurality of applicablealgorithms.
 13. The digital watermark embedding method according toclaim 9, wherein said superimposing portion selecting step divides thedata to be watermarked into the data areas in units of time-series dataframes, and said superimposing level determining step selects anddetermines beforehand the digital watermark embedding algorithm to beapplied to each of the data areas generated on the basis of the dataframes from among the plurality of applicable algorithms.
 14. Thedigital watermark embedding method according to claim 9, wherein saidsuperimposing portion selecting step divides the data to be watermarkedinto the data areas on the basis of space position information, and saidsuperimposing level determining step selects and determines beforehandthe digital watermark embedding algorithm to be applied to each of thedata areas generated on the basis of the space position information fromamong the plurality of applicable algorithms.
 15. The digital watermarkembedding method according to claim 9, wherein said superimposing leveldetermining step selects and determines beforehand the digital watermarkembedding algorithm to be applied to each of the data areas generated insaid superimposing portion selecting step from among the plurality ofapplicable algorithms, and the plurality of algorithms include aplurality of algorithms for embedding digital watermarks at differentdigital watermark embedding levels.
 16. The digital watermark embeddingmethod according to claim 9, wherein said superimposing portionselecting step performs data area division of data subjected to signaltransformation including at least one of filtering, encoding, orthogonaltransformation, and compression.
 17. A computer readable storage mediumwith computer readable instructions that when executed by a processorperform a digital watermark embedding process, comprising: asuperimposing portion selecting step of dividing each frame of data tobe watermarked into a plurality of data areas, said superimposingportion selecting step including determining borders of each data areabased on data characteristics of each data area in the frame; asuperimposing level determining step of selecting and determiningbeforehand which digital watermark embedding algorithm to apply to eachof the data areas in the frame generated in said superimposing portionselecting step from among a plurality of different applicable algorithmsbased on characteristics of each of the data areas in the frame; adigital watermark generating step of generating digital watermarkinformation based on additional information to be embedded as a digitalwatermark; a digital watermark level controlling step of generating, onthe basis of the digital watermark information generated in said digitalwatermark generating step, a digital watermark pattern in which thedigital watermark embedding algorithm determined in said superimposinglevel determining step is applied; and a digital watermark superimposingstep of embedding the digital watermark pattern output in said digitalwatermark level controlling step into the data to be watermarked.
 18. Adigital watermark embedding apparatus, comprising: a superimposingportion selecting unit configured to select and divide each frame ofdata to be watermarked into a plurality of data areas, saidsuperimposing portion selecting unit configured to determine borders ofeach data area based on data characteristics of each data area in theframe; a superimposing level determining unit configured to select anddetermine beforehand which digital watermark embedding algorithm toapply to each of the data areas in the frame generated by saidsuperimposing portion selecting unit from among a plurality of differentapplicable algorithms based on characteristics of each of the data areasin the frame; a digital watermark generating unit configured to generatedigital watermark information based on additional information to beembedded as a digital watermark; a digital watermark level controllingunit configured to generate, on the basis of the digital watermarkinformation generated by said digital watermark generating unit, adigital watermark pattern in which the digital watermark embeddingalgorithm determined by said superimposing level determining unit isapplied; and a digital watermark superimposing unit configured to embedthe digital watermark pattern output by said digital watermark levelcontrolling unit into the data to be watermarked.
 19. The digitalwatermark embedding apparatus according to claim 1, wherein thesuperimposing level determining means selects a different digitalwatermark embedding algorithm to apply to a first data area in the frameof data than a digital watermark embedding algorithm to apply to asecond data area in the frame of data.
 20. The method according to claim9, further comprising: selecting a different digital watermark embeddingalgorithm to apply to a first data area in the frame of data than adigital watermark embedding algorithm to apply to a second data area inthe frame of data.